As I had to draw some new icons tonight I thought I'd share some information that might be of use to some of you. The corner radius for appstore icons is a fraction of the width of the icon. If you want to do an internal rounded corner that matches the outer rounded corner, it is the same fraction - you can use this to make a correctly proportioned border around your icon. Here is the simple formula: cornerRadius = width X 0.15625 example: 512 * 0.15625 = 80 also, here is the full list (as of april 2011) of icon sizes required for the app store (i think you can get away with less than this but we do all sizes just to be safe) : 512, 114, 72, 58, 57, 50 and 29. here is the icon I was working on tonight, I didn't add the outer round edge to the edge of the icon as this is done automatically, and I think it is best to avoid doing one to prevent any fringing. hope this helps someone Nick Physmo.com - makers of Mos Speedrun
Oh, that would have been helpful to know when I was making the icon for Staunch Defense and wanted to use a boarder. I think I spent a fair while fooling around with screen shots to get try getting it right.
I've seen this number of an 80 pixel radius on several websites now, but I don't think it is correct. If you take any 512x512 icon and apply an 80 pixel radius to the corners, and then scale it down to 175x175 and compare it to the same icon on iTunes, for example, you will have several extra pixels around the corners vs. what iTunes gives you (much more than what might be considered rounding differences). If you use a 90 pixel radius though, then you get practically identical results (although the iTunes scaling seems to result in some dithering in the cases I tested). I can't recall who first told me to use a radius of90, but my icons are always perfectly trimmed that way. Unfortunately I can't find any Apple docs to confirm 90 (or 80 for that matter).
iOS icon template The radius on a 512x512 icon is closer to 85. To be safest, please use this excellent template: http://blog.cocoia.com/2010/iphone-4-icon-psd-file/ Also for some tips on how to make sure your resized icon looks as clean as possible, see my 10-minute screencast on icon design and resolution-independence: http://weheartgames.com/2010/06/screencast-app-icon-design-and-resolution-independence/
